diff --git a/ChangeLog b/ChangeLog
index 8ee9546f7f..c449f21764 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Sat Jun 23 14:29:25 2012  Tanaka Akira  <akr@fsij.org>
+
+	* internal.h (rb_execarg): add chdir_given and chdir_dir fields.
+
+	* process.c (EXEC_OPTION_CHDIR): removed.
+	  (mark_exec_arg): mark chdir_dir field.
+	  (rb_execarg_addopt): update the new fields, instead of options array.
+	  (rb_execarg_run_options): use the new fields.
+
 Sat Jun 23 13:20:47 2012  Tanaka Akira  <akr@fsij.org>
 
 	* internal.h (rb_execarg): add close_others_given, close_others_do and
diff --git a/internal.h b/internal.h
index 140df9894f..b6c7dda7a9 100644
--- a/internal.h
+++ b/internal.h
@@ -182,9 +182,11 @@ struct rb_execarg {
     unsigned unsetenv_others_do : 1;
     unsigned close_others_given : 1;
     unsigned close_others_do : 1;
+    unsigned chdir_given : 1;
     pid_t pgroup_pgid; /* asis(-1), new pgroup(0), specified pgroup (0<V). */
     mode_t umask_mask;
     int close_others_maxhint;
+    VALUE chdir_dir;
 };
 
 /* argv_str contains extra two elements.
diff --git a/process.c b/process.c
index 155186f067..bc0f5895f3 100644
--- a/process.c
+++ b/process.c
@@ -1256,7 +1256,6 @@ rb_proc_exec(const char *str)
 enum {
     EXEC_OPTION_RLIMIT,
     EXEC_OPTION_ENV,
-    EXEC_OPTION_CHDIR,
     EXEC_OPTION_DUP2,
     EXEC_OPTION_CLOSE,
     EXEC_OPTION_OPEN,
@@ -1281,6 +1280,7 @@ mark_exec_arg(void *ptr)
     rb_gc_mark(eargp->envp_str);
     rb_gc_mark(eargp->envp_buf);
     rb_gc_mark(eargp->dup2_tmpbuf);
+    rb_gc_mark(eargp->chdir_dir);
 }
 
 static void
@@ -1622,12 +1622,12 @@ rb_execarg_addopt(VALUE execarg_obj, VALUE key, VALUE val)
             eargp->unsetenv_others_do = RTEST(val) ? 1 : 0;
         }
         else if (id == rb_intern("chdir")) {
-            if (!NIL_P(rb_ary_entry(options, EXEC_OPTION_CHDIR))) {
+            if (eargp->chdir_given) {
                 rb_raise(rb_eArgError, "chdir option specified twice");
             }
             FilePathValue(val);
-            rb_ary_store(options, EXEC_OPTION_CHDIR,
-                                  hide_obj(rb_str_dup(val)));
+            eargp->chdir_given = 1;
+            eargp->chdir_dir = hide_obj(rb_str_dup(val));
         }
         else if (id == rb_intern("umask")) {
 	    mode_t cmask = NUM2MODET(val);
@@ -2818,15 +2818,14 @@ rb_execarg_run_options(const struct rb_execarg *eargp, struct rb_execarg *sargp,
             return -1;
     }
 
-    obj = rb_ary_entry(options, EXEC_OPTION_CHDIR);
-    if (!NIL_P(obj)) {
+    if (eargp->chdir_given) {
         if (sargp) {
             char *cwd = my_getcwd();
-            rb_ary_store(sargp->options, EXEC_OPTION_CHDIR,
-                         hide_obj(rb_str_new2(cwd)));
+            sargp->chdir_given = 1;
+            sargp->chdir_dir = hide_obj(rb_str_new2(cwd));
             xfree(cwd);
         }
-        if (chdir(RSTRING_PTR(obj)) == -1) { /* async-signal-safe */
+        if (chdir(RSTRING_PTR(eargp->chdir_dir)) == -1) { /* async-signal-safe */
             ERRMSG("chdir");
             return -1;
         }